The present invention relates to motion control systems. More particularly, the present invention relates to a method and system for estimating a speed of a moving member in the motion control system.
In many motion control systems (rotary or linear), it is necessary to know the speed or velocity of a moving member in order to properly control the moving member. Typically, speed or velocity is determined as a function of displacement of the moving member. For instance, a position sensor, such as an encoder, provides a periodic output signal as a function of displacement. A first method of determining speed of the moving member includes counting the number of occurrences (e.g., edges of a square wave) in a selected time period. This technique can provide accurate estimates of the speed of the moving member particularly when higher speeds are present. However, when the moving member is traveling at a slow rate of speed, less accurate estimates are obtained.
A second technique of speed estimation includes measuring the time between successive occurrences of the periodic output signal. This technique provides accurate estimates of the velocity of the moving member when the moving member is traveling slowly. However, at higher rates of speed, less accurate results are obtained.
Accordingly, there is an ongoing need to provide an accurate system and method for estimating the speed of a moving member at slow and high rates of speed.